This research project will analyze how William Harvey's discovery of the circulation of the blood proved the inspiration for an Oxford group of physiologists which, during the period 1640-1680, elucidated the chemical nature of the air, the function of respiration, the composition of the blood, and the origins of animal heat as a process of combustion analogous to fire. Research will show how this group, including Thomas Willis, Robert Boyle, Richard Lower, Robert Hooke and John Mayow among others, were brought together by the institutional structure and historical circumstances of mid-seventeenth century Oxford. They formed ties of friendship, common assumptions about natural philosophy, common beliefs about important physiological problems, and mutually acceptable ways of answering these problems by appeal to laboratory techniques developed in concert. Their scientific innovations will be shown to be a direct outcome of shared membership in this group. It will be suggested that the analysis of this group, in the way in which it links conceptual change to an institutional and social network, offers an important new historiographic model of scientific change capable of application to a large number of episodes of scientific advance.